In general, a phantom is used to calibrate and/or verify the accuracy of nuclear medical imaging devices such as PET scanners. In essence, a phantom is a body with known shape and uniform distribution of radiation activity throughout the body. Thus, by imaging the phantom with its known geometry and radiation distribution, the accuracy of the software used to assemble the various tomographic slices acquired by the imaging apparatus into three-dimensional representations of a patient's region of interest can be assessed and, if necessary, the various apparatus settings can be adjusted. More specifically, imaging a phantom with uniform distribution of radioactivity allows a set of calibration coefficients to be developed to compensate for non-uniformity of the scintillation materials and/or detector components in the PET scanner.
Recently, a fully integrated magnetic resonance/PET scanner has been developed, which integrated scanner allows for simultaneous MR and PET imaging (see, e.g., U.S. Pub. No. 2007/0055127, published Mar. 8, 2007 and incorporated herein by reference). Such a scanner requires a dedicated phantom which, in addition to facilitating quality control assessment of the PET scanning functionality of the machine, facilitates a determination of the extent to which operating the MR functionality of the machine influences the PET signals acquired by the machine. A conventional phantom will not work for this purpose because the MR coil of the scanner has to experience a certain load in order to dampen the resonance peak sufficiently, even when maximum RF power is applied to the coil. Otherwise, if the MR coil is not loaded when maximum RF power is applied, too much current will be developed in the MR resonance circuit, and that current could potentially be high enough to destroy the MR coil itself.